High-throughput assays to measure intracellular protein aggregation using fluorescence resonance energy transfer (FRET) are known in the art, and have been successfully used to screen for inhibitors of aggregation. For instance, U.S. Pat. No. 7,803,559 teaches a high-throughput assay to measure intracellular polyglutamine protein aggregation using FRET. Similar assays designed to measure intracellular tau aggregation have also been described. For example, see Kfoury et al. (J Biol Chem 2012). While these methods are capable of detecting recombinant protein, the lower limit of detection for these assays precludes their usefulness with biological samples such as blood and CSF, where the concentration of the protein aggregate “seed” is orders of magnitude lower. Hence, there is a need in the art for a method to detect protein aggregates in biological samples.